neuronal comms

• sensory receptors are specialised cells that can detect changes in our surroundings. Most sensory receptors are energy transducers that convert one form of energy to another
• Each type of transducer is adapted to detect changes in a particular form of energy. This may be a change in light levels, a change in pressure on the skin or one of many energy changers. Some receptors detect the presence of chemicals
• Each change in the environment, whether it is a change in the energy level or the presence of a new chemical, is called a stimulus. Whatever the stimulus, the sensory receptors respond by creating a signal in the form of electrical energy called a nerve impulse
• what is the sensory receptor for a change in light intensity?

  Light sensitive cells, rods and cones, in the retina
• What is the energy change involved when there is a light intensity change?

  Light to electrical
• What is the sensory receptor when there is a change in temperature?

  Temperature receptors in the skin and hypothalamus
• What is the energy change involved when there is a change in temperature?

  Heat to electrical
• What is the sensory receptor when there is a change in pressure on the skin?

  Pacinian corpuscles in the skin
• What is the energy change if there is a change in pressure on the skin?

  Movement to electrical
• What is the sensory receptor if there is a change in sound?

  Vibration receptors in the cochlea of the ear
• What is the energy changed involved when there is a change in sound?

  Movement into electrical
• what is the sensory receptor when there is movement from the surroundings around the ear?

  Hair cells in the inner ear
• What is the energy change when there is movement from the surroundings around the ear?

  Movement to electrical
• What is the sensory receptor when there is a change in the chemicals in the air?

  Olfactory cells in the epithelium lining the nose
• What is the energy change when there is a change in chemicals in the air?

  The olfactory cells in the epithelium of the nose detect the presence of chemicals and creates an electrical nerve impulse
• What are the sensory receptor(s) which detect the chemicals in food?

  Chemical receptors in taste buds on the tongue
• What is the energy change involved in the body detecting the chemicals in food?

  The chemical receptors in the taste buds of the tongue detect the presence of a chemical and produces an electrical nerve impulse
• a pacinian corpuscle is a pressure sensor that detects change in pressure on the skin
• The pacinian corpuscles are oval shaped structures which consist of a series of concentric rings of connective tissues that are wrapped around the end of the nerves. When pressure on the kin changes, this deforms the rings of connective tissue which push against the nerve ending. The corpuscle is sensitive only to changes in pressure which deforms the rings of connective tissue- thus if pressure is constant then they stop responding.
• when a neurone cell is inactive, the cell membrane is said to be polarised. That is negatively charged inside, compared to the outside.
• A nerve impulse is created by altering the permeability of the nerve cell membrane to sodium ions. This is achieved by opening the sodium ion channels. As the sodium ion channels open, the membrane permeability is increased and Na ions can move across the membrane down their concentration gradient into the cell. This movement of ions across the membranes creates a change in potential difference across the membrane.
• If the inside of the nerve cell becomes less negative than its outside, then it is depolarised. The change in potential across a receptor is often called a generator potential.
• If a small stimulus is dtected, only a few Na channels will open. The larger the stiumulus, then more gated Na channels open. If enough gates are opened and enough sodium ions enter the cell the Potential difference across the cell membrane changes and will emit an action potential.